Split DefaultSmartWalletService into domain services

[tomas-martins-crossmint]

DefaultSmartWalletService was a single class implementing all wallet operations across every domain. It now delegates to six standalone services, each owning one domain, and SmartWalletService becomes a protocol composition.

Changes

• SmartWalletService — now a protocol composition of WalletService, TransactionService, TransferService, BalanceService, NFTService, and SignatureService; previously a single flat protocol with all methods
• DefaultSmartWalletService — thin facade holding one instance of each domain service and delegating every method; contains no logic of its own
• DefaultWalletService, DefaultTransactionService, DefaultTransferService, DefaultBalanceService, DefaultNFTService, DefaultSignatureService — new standalone service structs, each responsible for one domain, grouped under Sources/Wallet/Data/Services/<Domain>/
• AuthManagerProviding — internal protocol with a default authHeaders implementation, adopted by all six services to remove the duplication
• TransactionRequestExecuting — internal protocol with a default executeTransactionRequest implementation, adopted by the three services that dispatch on-chain transactions
• CreateSignatureRequest.Body — replaces SignatureRequestProtocol existential and the old ResponseType enum; each case carries its associated request value directly
• TransferTokenRequest — replaces the six-parameter transferToken method signature with a params struct
• Endpoints.swift — centralises all URL path construction into static Endpoint factory methods; previously built inline in each service method

[greptile-apps]

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
Sources/Wallet/Data/Services/DefaultTransferService.swift:6-10
The synthesized `Encodable` for `TransferBody` encodes `nil` optionals as `"signer": null`, whereas the original hand-rolled implementation used `encodeIfPresent`, which omits the key entirely. If the transfer API rejects an explicit `null` for `signer`, every call without a signer will fail after this refactor.

```suggestion
private struct TransferBody: Encodable {
    let recipient: String
    let amount: String
    let signer: String?

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(recipient, forKey: .recipient)
        try container.encode(amount, forKey: .amount)
        try container.encodeIfPresent(signer, forKey: .signer)
    }

    private enum CodingKeys: String, CodingKey { case recipient, amount, signer }
}
```

### Issue 2 of 2
Sources/CrossmintService/JSONCoder.swift:26-35
`try?` silently discards the original `DecodingError`, so all failures surface only as the generic caller-supplied error. Logging the underlying error before throwing preserves debuggability without changing the public API.

```suggestion
    func decodeOrThrow<T: Decodable, E: Error>(
        _ type: T.Type,
        from data: Data,
        onFailure: @autoclosure () -> E
    ) throws(E) -> T {
        do {
            return try decode(type, from: data)
        } catch {
            print("[JSONCoder.decodeOrThrow] Failed to decode \(T.self): \(error)")
            throw onFailure()
        }
    }
```

_{Reviews (1): Last reviewed commit: "Address afeight-review: extract Endpoint..." | Re-trigger Greptile}

[greptile-apps]

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
Sources/Wallet/Data/Services/DefaultTransferService.swift:6-10
The new `TransferBody` struct loses the `encodeIfPresent` behavior that the old inline `Body` had for the optional `signer` field. Swift's synthesised `Encodable` encodes `nil` optionals as `"signer": null` in JSON, whereas the original code used `encodeIfPresent` which omitted the key entirely. If the API treats a missing key differently from `null` — for example rejecting the request or routing it differently — this silent change will cause failures for every transfer call where `signer` is not provided.

```suggestion
private struct TransferBody: Encodable {
    let recipient: String
    let amount: String
    let signer: String?

    private enum CodingKeys: String, CodingKey { case recipient, amount, signer }

    func encode(to encoder: Encoder) throws {
        var c = encoder.container(keyedBy: CodingKeys.self)
        try c.encode(recipient, forKey: .recipient)
        try c.encode(amount, forKey: .amount)
        try c.encodeIfPresent(signer, forKey: .signer)
    }
}
```

### Issue 2 of 2
Sources/CrossmintService/JSONCoder.swift:26-35
`decodeOrThrow` silently discards the underlying decode error via `try?`, replacing it with the generic `onFailure` value. This makes it impossible to tell from crash reports or logs which field failed to decode and why. Consider logging or wrapping the original error before discarding it, or at minimum keeping the `CrossmintServiceError` available for internal diagnostics while still surfacing the domain-specific error to callers.

_{Reviews (1): Last reviewed commit: "Address afeight-review: extract Endpoint..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (2): Last reviewed commit: "extract executeTransactionRequest into T..." | Re-trigger Greptile}